scholarly journals A Switched Approach to Image-Based Stabilization for Nonholonomic Mobile Robots with Field-of-View Constraints

2021 ◽  
Vol 11 (22) ◽  
pp. 10895
Author(s):  
Yao Huang
Keyword(s):  
Mobile Robot ◽  
Visual Servoing ◽  
Nonholonomic Constraint ◽  
Focal Length ◽  
Field Of View ◽  
System Model ◽  
Nonholonomic Mobile Robots ◽  
Nonholonomic Mobile Robot ◽  
Polar Coordinate ◽  
Simulation Results

This paper presents a switched visual servoing strategy for maneuvering the nonholonomic mobile robot to the desired configuration while keeping the tracked image points in the vision of the camera. Firstly, a pure backward motion and a pure rotational motion are applied to the mobile robot in succession. Thus, the principle point and the scaled focal length in x direction of the camera are identified through the visual feedback from a fixed onboard camera. Secondly, the identified parameters are used to build the system model in polar-coordinate representation. Then an adaptive non-smooth controller is designed to maneuver the mobile robot to the desired configuration under the nonholonomic constraint. And a switched strategy which consists of two image-based controllers is utilized for keeping the features in the field-of-view. Simulation results are presented to validate the effectiveness of the proposed approach.

scholarly journals Trajectory Tracking with Input Constraint based on LMI Approach of a Nonholonomic Mobile Robot

2021 ◽  
Vol 5 (1) ◽  
Author(s):  
Auliya Nabila ◽  
Trihastuti Agustinah
Keyword(s):  
Mobile Robot ◽  
Tracking Control ◽  
State Feedback ◽  
Reference Trajectory ◽  
Input Constraint ◽  
Lmi Approach ◽  
Nonholonomic Mobile Robot ◽  
Mode Of Transportation ◽  
Simulation Results ◽  
Reference Trajectories

Nonholonomic Mobile Robot (NMR) is a mode of transportation that is widely used in industry. To achieve flexibility in carrying out its duties, an adequate control system is needed in transportation arrangements so that it is used as an object of research. The problem that is taken in this study is about tracking control for several reference trajectories with input constraint.To solve this problem two controllers were designed, kinematics controller and dynamics controller. Kinematics controller is designed so that the additional speed converges to the desired speed by adjusting the gain value , , and . Dynamic controller is designed using  performance to overcome the input constraint and the Lyapunoc inequality is soleved by Linear Matric Inequalities (LMI) so the gain state-feedback can be obtained. Simulation results show that the designed controller is capable of tracking according to the reference trajectory with input constraint given.

scholarly journals Real-Time Inverse Optimal Neural Control for Image Based Visual Servoing with Nonholonomic Mobile Robots

2015 ◽  
Vol 2015 ◽  
pp. 1-12 ◽  
Author(s):  
Carlos López-Franco ◽  
Michel López-Franco ◽  
Alma Y. Alanis ◽  
Javier Gómez-Avila ◽  
Nancy Arana-Daniel
Keyword(s):  
Real Time ◽  
Visual Servoing ◽  
Neural Control ◽  
Parameter Uncertainties ◽  
Visual Sensor ◽  
External Disturbances ◽  
Neural Controller ◽  
Nonholonomic Mobile Robots ◽  
Nonholonomic Mobile Robot ◽  
High Order Neural Network

We present an inverse optimal neural controller for a nonholonomic mobile robot with parameter uncertainties and unknown external disturbances. The neural controller is based on a discrete-time recurrent high order neural network (RHONN) trained with an extended Kalman filter. The reference velocities for the neural controller are obtained with a visual sensor. The effectiveness of the proposed approach is tested by simulations and real-time experiments.

scholarly journals Three-Step Epipolar-Based Visual Servoing for Nonholonomic Robot with FOV Constraint

2014 ◽  
Vol 2014 ◽  
pp. 1-14
Author(s):  
Yang Xu ◽  
Jun Peng ◽  
Wentao Yu ◽  
Yuan Fang ◽  
Weirong Liu
Keyword(s):  
Output Feedback ◽  
Visual Servoing ◽  
Feature Points ◽  
Efficient Technology ◽  
Nonholonomic Mobile Robots ◽  
Current Configuration ◽  
Control Scheme ◽  
Simulation Results ◽  
The Difference ◽  
Configuration Simulation

Image-based visual servoing for nonholonomic mobile robots using epipolar geometry is an efficient technology for visual servoing problem. An improved visual servoing strategy, namely, three-step epipolar-based visual servoing, is developed for the nonholonomic robot in this paper. The proposed strategy can keep the robot meeting FOV constraint without any 3D reconstruction. Moreover, the trajectory planned by this strategy is shorter than the existing strategies. The mobile robot can reach the desired configuration with exponential converge. The control scheme in this paper is divided into three steps. Firstly, by using the difference of epipoles as feedback, the robot rotates to make the current configuration and desired configuration in the same orientation. Then, by using a linear input-output feedback, the epipoles are zeroed so as to align the robot with the goal. Finally, by using the difference of feature points, the robot reaches the desired configuration. Simulation results and experimental results are given to illustrate the effectiveness of the proposed control scheme.

scholarly journals The Heading Weight Function: A Novel LiDAR-Based Local Planner for Nonholonomic Mobile Robots

Sensors ◽  
2019 ◽  
Vol 19 (16) ◽  
pp. 3606 ◽  
Author(s):  
Harik ◽  
Korsaeth
Keyword(s):  
Weight Function ◽  
Light Detection And Ranging ◽  
Polar Coordinate System ◽  
The Novel ◽  
Digital Environment ◽  
Nonholonomic Mobile Robots ◽  
Nonholonomic Mobile Robot ◽  
Polar Coordinate ◽  
Angular Velocities ◽  
Novel Method

In this paper, we present a novel method for obstacle avoidance designed for a nonholonomic mobile robot. The method relies on light detection and ranging (LiDAR) readings, which are mapped into a polar coordinate system. Obstacles are taken into consideration when they are within a predefined radius from the robot. A central part of the approach is a new Heading Weight Function (HWF), in which the beams within the aperture angle of the LiDAR are virtually weighted in order to generate the best trajectory candidate for the robot. The HWF is designed to find a solution also in the case of a local-minima situation. The function is coupled with the robot’s controller in order to provide both linear and angular velocities. We tested the method both by simulations in a digital environment with a range of different static obstacles, and in a real, experimental environment including static and dynamic obstacles. The results showed that when utilizing the novel HWF, the robot was able to navigate safely toward the target while avoiding all obstacles included in the tests. Our findings thus show that it is possible for a robot to navigate safely in a populated environment using this method, and that sufficient efficiency in navigation may be obtained without basing the method on a global planner. This is particularly promising for navigation challenges occurring in unknown environments where models of the world cannot be obtained.

Dynamic Analysis and Quasi-Sliding Mode Control of Mobile Robot

2012 ◽  
Vol 433-440 ◽  
pp. 3168-3174
Author(s):  
Hong Mei Wang ◽  
Ming Lu Zhang ◽  
Guang Zhu Meng
Keyword(s):  
Sliding Mode Control ◽  
Mobile Robot ◽  
Sliding Mode ◽  
Sliding Mode Controller ◽  
Control Torque ◽  
Nonholonomic Mobile Robot ◽  
Mode Control ◽  
Angular Velocities ◽  
Fine Control ◽  
Simulation Results

To avoid the chattering disadvantage of sliding-mode control (SMC), in this paper, a quasi-sliding mode controller is proposed for real-time fine control of a nonholonomic mobile robot. First, the dynamics of mobile robot is analyzed by Lagrangian formula. Then, the quasi-sliding mode controller is used to generate the control torque that drives the mobile robot, such that the linear and angular velocities of the mobile robot follow the desired velocities. At last, computer simulation results confirm the effectives of SMC.

A High Resolution Scanning Microscope

1968 ◽  
Vol 26 ◽  
pp. 356-357
Author(s):  
A. V. Crewe ◽  
J. Wall ◽  
L. M. Welter
Keyword(s):  
High Resolution ◽  
Field Emission ◽  
Spherical Aberration ◽  
Focal Length ◽  
Spot Size ◽  
Emission Source ◽  
Field Of View ◽  
Scanning Microscope ◽  
Magnetic Lens ◽  
High Quality

A scanning microscope using a field emission source has been described elsewhere. This microscope has now been improved by replacing the single magnetic lens with a high quality lens of the type described by Ruska. This lens has a focal length of 1 mm and a spherical aberration coefficient of 0.5 mm. The final spot size, and therefore the microscope resolution, is limited by the aberration of this lens to about 6 Å.The lens has been constructed very carefully, maintaining a tolerance of + 1 μ on all critical surfaces. The gun is prealigned on the lens to form a compact unit. The only mechanical adjustments are those which control the specimen and the tip positions. The microscope can be used in two modes. With the lens off and the gun focused on the specimen, the resolution is 250 Å over an undistorted field of view of 2 mm. With the lens on,the resolution is 20 Å or better over a field of view of 40 microns. The magnification can be accurately varied by attenuating the raster current.

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